I uninstalled the game to make room for other things, so i cannot check if this is accurate, but I believe you need to hit the enemy into the air while you are on the ground and stay in place. I also could not get the achievement in the practice mode. It could actually be a bug, though.

I got the hat trick but but not the others. I used the basic launching attack on the second level and just spammed it on one enemy. Nothing fancy. I didn't even know there was an achievement. I was just being cheap!